Packet data networks are widely used to link various types of network elements, such as personal computers, servers, network telephones, Internet appliances, and so forth. Examples of packet data networks include private networks (such as local area networks or wide area networks) and public networks (such as the Internet). Common forms of communications between network elements across packet data networks include electronic mail, file transfer, web browsing, and other exchanges of data. More recently, with the increased capacity and reliability of packet data networks, audio communications (such as voice communications), video communications (such as video conferencing), and other forms of real-time interactive or streaming communications are becoming more common in packet data networks. Traditionally, packet-data networks have been implemented on wired networks.
With advancements in wireless communications networks, efficient packet-switched communications in wireless networks have also become possible. Traditionally, wireless communications networks have been implemented as circuit-switched networks. In a circuit-switched network, a channel between two end points (e.g., two mobile stations) is occupied for the duration of the connection between the end points. Such a connection is optimal for communications that are relatively continuous, such as speech. However, circuit-switched networks are not very efficient for packet-switched communications such as e-mail, web browsing, and the like.
Several packet-switched wireless protocols have been proposed to provide more efficient packet-switched communications between a mobile station and a packet data network, such as an Internet Protocol (IP) network. One such protocol is the General Packet Radio Service (GPRS) protocol, which complements existing GSM (Global System for Mobile) communications systems. Other technologies that build upon GPRS are the Enhanced GPRS (EGPRS) technology (also referred to as Enhanced Data Rate for Global Evolution or EDGE) and EGPRS COMPACT (or EDGE COMPACT) technology, which offer higher data rates and complement GSM and IS-136 systems. Another type of wireless network that can support efficient packet-switched communications is a UMTS (Universal Mobile Telecommunication System) wireless network, which is based on the Wideband Code-Division Multiple Access (W-CDMA) protocol.
Circuit-switched wireless technology is a relatively mature technology that employs various techniques to enhance reliability and performance of circuit-switched communications of speech. For example, according to UMTS, unequal error protection (UEP) of speech bits is used to achieve optimum mean opinion scores (MOS) when using adaptive multi-rate (AMR) speech codecs. Although such mechanisms have been provided for circuit-switched speech communications, the same does not hold true for packet-switched speech communications in a wireless network. As a result, optimum performance of packet-switched communications of speech and/or other forms of real-time data in wireless networks may not be readily achievable.